Properties of Higher Plant Mitochondria. I. Isolation and Some Characteristics of Tightly-coupled Mitochondria from Dark-grown Mung Bean Hypocotyls

The mitochondria isolated from dark-grown mung bean hypocotyls oxidize succinate, l-malate, and externally added reduced nicotine adenine dinucleotide (NADH) with good respiratory control. While the pattern of respiration resembles that of animal mitochondria, there are 4 basic differences between the respiratory properties of mung bean and animal mitochondria: A) the ability to oxidize NADH, B) the pattern of succinate and malate oxidation, C) the rate of oxygen uptake, and D) the adenosine-5'-diphosphate to oxygen ratios.The apparent ;Km' for malate of mung bean mitochondria is about one order higher than that expected from malic dehydrogenase in animal mitochondria, whereas the affinity for phosphate is about 5 times higher with plant mitochondria than rat-liver mitochondria. While the half-maximal stimulation of respiration by adenosine-5'-diphosphate is practically identical to that of animal mitochondria, higher concentrations of adenosine-5'-diphosphate cause some decrease in its stimulating action.